Power supply system for vacuum tube amplieying devices



Feb. 14, 1933. v. M. GRAHAM ET AL I 1,897,556

POWER SUPPLY SYSTEM FOR VACUUM TUBE AMPLIFYING DEVICES Filed March 5,1928 INVENTOR VIFZGlLM. GRAHAM BY WINFQED T POWELL ATTOR iii PatentedFeb. 14, 1933' UNITED STATES PATENT OFFICE VIRGIL M. GRAHAM AND WINFREDT. POWELL, OF ROCHESTER, NEW YORK, ASSIGNORS TO THE' STROMBERG-CARLSONTELEPHONE MANUFACTURING COMPANY, OF ROCHESTER, NEW YORK, A CORPORATIONOF NEW YORK 7 POWER SUPPLY SYSTEM FOR VACUUM TUBE AMPLIFYING DEVICESApplication filed March 5,

This invention relates to rectifying systems and more particularly torectifying systems utilized in connection with vacuum tube amplifiers.It hasbeen discovered in rectifying systems where a large voltage outputis required that the rectifying tubes are frequently of very short lifedue to the fact that a very high voltage is applied to the anodes of therectifiers before the filaments have been heated to full brilliancy withthe result that it causes a certain stripping action whereby thematerial of the filaments is rapidly eroded so that they quicklydeteriorate. As a remedy for this defect it has been discovered that ifthe anode voltage is not applied to the anodes f the rectifiers untilthe filaments have been lighted to full brilliancy this stripping actionis avoided and the expected life of the tubes is obtained.

The main feature of the invention resides in the provision of means in arectifying system utilized in connection with a vacuum tube amplifierfor preventing the anode voltage from being applied to the anodes untilthe filaments have been heated to approximately 90% of their normaloperating temperature.

For a clearer understanding of the invention reference is made to thedrawing in which a portion thereof above the broken line represents a.portion of a radio receiver having a radio frequency amplifying stage, adetector and. two stages of audio amplification while a loud speaker isassociated with the output stage of the last audio amplifier. Theportion of the drawing below the broken line represents a rectifyingsystem for supplying plate voltage to the vacuum tubes of the radioreceiver and an additional set of rectifiers for furnishing the heatingcurrent to the filaments of the vacuum tubes or electron dischargedevices.

In the drawing the numeral 1 designates a vacuum tube in a radiofrequency stage of a radio receiver while the numeral 2 designates adetector, and the numerals 3 and 4 indicate vacuum tubes in the audioamplifying stage of a radio receiver. The circuits of the radio receiverare not completely shown but only those portions relating to the 1928.Serial No. 259,017.

circuits for heating the filaments of these vacuum tubes and forapplying a plate voltage to the anodes thereof. The output circuit ofthe last audio stage includes a loud speaker 5 together with the usualaudio filter associated therewith. The circuits and operation of theradio receiver may be similar to that of any of the well-known types ofradio receivers now on the market which utilize rectified or partiallyrectified alternating current for heating the filaments of the vacuumtubes in the several stages thereof.

The rectifying system of this invention includes the primary winding 6of a transformer connected by suitable switching means in series with asource of alternating current (not shown). This transformer is providedwith a plurality of secondary windings, one of which designated 7furnishes heating current for heating the filaments 8 and 9 of therectifier tubes which furnish the plate or anode voltage to several ofthe vacuum tubes of the radio receiver. The secondary winding 8 of thistransformer has its ends connected to the anodes 10 and 11 of theserectifiers and its intermediate point connected through the choke coils12 and 13 and thence through resistance 20, the resistance of either thewinding of relay 21 or of relay 29, the resistance 15 over conductors 46and 16 to a point on the filament heating system. It will be understoodthat the choke coils 12 and 13 serve with condensers 17 18 and 19 as amulti-stage filter for filtering out the ripple or alternating currentcomponent in the rectified current. The resistances 15, 20 and theresistance of the winding of the slow releasing relay 21 or of thesubstitute relay winding 29 operate by the drop in potential method toapply the necessary different voltages to the anodes of several of thevacuum tubes. The secondary winding 22 of the mentioned transformer isconnected in series with the filaments 23 and 24 of the rectifying tubes60 and 61 which furnish the rectified current for heating the filamentsof the several vacuum tubes of the radio receiver.

The secondary winding 25 of this transformer has its ends respectivelyconnected 7 21 and thence to the lower end of the windhas beendiscovered that .ductors 33 and ing 25. The purpose of the normallyopened contacts 28, 31 and of the normally closed contacts 30, 32 willbe set forth hereinafter.

It will be noted that the filaments of the vacuum .tubes or electrondischarge devices 1, 2 and 3 are connected. in series to the con- 7 34,the conductor 33 being connected through the inductances 35 and 36 to anintermediate point on a secondary winding 25 and the conductor 34 beingconnected through the choke coils 37 and 38 to .a point on the filamentsystem of filaments 23 and 24. The choke coils 35, 36, 37 and 38together with the condensers 39 and 40 form a two-stage filter forfiltering out a ripple or alternating current component. The secondarywinding 41 of the transformer has its ends connected in series with theconductors. 42 and 43 which in turn serially include the filament of thevacuum tube 4 inthe last audio stage. A potentiometer 45 is connectedacross the secondary winding 41 in such a manner that its adjustablemember 44 which is connected to the negative lead 33, may be adjusted tobalance out any hum which otherwise would be introduced into thefilament system of the vacuum tube 4.

The rectifier tubes 60 and 61 which supply the heating current to thefilaments of the vacuum tubes 1, 2 and 3 are of the typein which theelectrodes operate in a gas. It if a voltage isap" plied to he anodes 26and 27 before the filaments such as 23 and 24 are heated toapproximately 90% of their normal operating temperature there is atendency for an arc to form in the rectifier tubes which erodes thefilaments and in a relatively short time causes them to deteriorate sothat their life is very much less than their normal rating. In order toovercome this defect slow releasing relay 21 and relay 29 are introducedinto the network of the power supply device to hold the circuits of theanodes 26 and 27 open for a sufficient period topermit the filaments 23and 24 to approach 90% of their normal heating temperature.

When it is desired to operate the radio receiver a switch (not shown) isclosed'to connect the primary winding 6 of the transformer in circuitwith the alternating current source. As soon as this takes place thefilaments 8 and9 heat up and the rectifier tubes of which they are apart begin to rectify the alternating current and the two-stage filtersacross the conductors 46 and 47 function to filter out the alternatingcurrent component. Rectified current flowing in conductors 46 and 47operates the slow releasing relay 21 in a circuit partially described asincluding resistance 15, continuity spring 7 and back contact 48 ofrelay29, winding of relay 21 and thence'to conductor 47. The relay 21attracts its armatures and at the contacts 30 and 32 opens the circuitswhich supply the potential to anodes 26 and 27. As soon as the righthand armature and contact of the relay 21 is-closed an operating circuitfor the relay29 is completed from. the conductor 46, resistance 15,right-hand contact and armature'of relay 21, winding of relay 29,resistance20 and thence to conductor 47 As soon as the relay 29 isoperated it closes a locking circuit for itself through its left handarmature and continuity spring which renders the operation of the relay29 independent of the operation of the slow releasing relay 21. Alsowith the relay 29 operated contacts 28 and 31 in the plate circuits ofthe anodes26 and 27 are closed but these circuits are ineffective untilthe slow releasing relay 21 has retracted its armatures which it startsto do as soon as the relay 29is operated. It will thus be seen that therelays 21 and 29 measure a predetermined interval of time after thepower device is connected in circuit with the alternating current sourceso that the filaments 23 and 24 have an opportunity to become heatedbefore the anode circuits including the anodes 26 and 27 are closed.This time interval may be explained as follows: The relay 21 requires ashort period of time before it fully attracts its armatures. Thereafterthe relay 29 requires another interval of time before it fully attractsits armatures and when it has done so. it opens the operating circuit ofthe relay 21 which requires a relatively long interval for it to releaseits armatures. tervals of time are long enough to permit the filamentsto become heated and during these time intervals the anode circuits areopened either at the back contacts 30 and 32 of the relay 21 or at thenormally open contacts 28 and 31 of the relay 29. In order to providethe proper drop in potential across conductors 53 and 54 it has beencustomary to connect the points 50 and 52 with a resistance ofthe'proper value. In the present arrangements the resistance of thewinding of relay 29 replaces the resistance formerly used and yetprovides the proper voltage across the conductors 53 and 54.

What we claim, is:

1. In combination, a circuit network, a source of alternating current, arectifier unit for furnishing voltages of different values to saidcircuit network from said source, a

These three insecond rectifier unit including a cathode and an anode, acathode circuit including said cathode, an anode circuit including saidanode for furnishing current to said circuit network, and meanscontrolled by said first rectifier unit for disabling said anode circuituntil said rectifier cathode is heated.

2. In a rectifying system, a source of current to be rectified, analternating current rectifier unit including a rectifier tube having afilamentary cathode and an anode operating in an atmosphere of gas,circuits including said cathode and said anode, a second rectifier unit,and means operated by said second rectifier unit for completing saidanode circuit whereby said cathode is protected.

3. In a rectifying system, a source of current to be rectified, arectifier unit connected to said source of current, an output circuitfor said rectifier unit, resistance units connected across said outputcircuit, a second alternating current rectifier unit including a tubehaving a cathode and an anode, a circuit including said cathodeelectrically connected to said source of current, a work circuitincluding said anode, and a relay connected in series with one of saidresistance units for controlling said anode circuit whereby said cathodeis protected.

4. In a rectifier system, a source of current to be rectified, arectifier unit connected to said source of current, an output circuitfor said rectifiercunit, resistance units connected to said outputcircuit, a slow relay connected in series with one of said resistanceunits across said output circuit, a second rectifier unit including atube having a cathode and an anode, a circuit including said anodeelectrically connected to said source of current, a work circuitincluding said anode, and means including said slow relay forcontrolling said anode circuit.

5. In a rectifying system, a source of current to be rectified, arectifier unit connected to said source of current, an output circuitfor said unit, resistance units connected to said output circuit, a slowreleasing relay normally connected in series with one of said resistanceunits across said output circuit, a second rectifier unit including atube having a cathode and an anode, a circuit including said cathodeelectrically connected to said source of current, an anode circuitincluding said anode, a second relay cooperating with and arranged to besubstituted for said slow relay for controlling said anode circuit.

6. In a rectifying system, a source of current to be rectified, arectifier unit connected to said source of current, an output circuitfor said unit, resistance units connected to said output circuit, a slowreleasing relay normally connected in series with at least one of saidresistance units across said output circuit, a second rectifier unitincluding a tube having a cathode and an anode, a circuit including saidcathode electrically connected to said source of current, an anodecircuit including said anode, and a second relay cooperating with andarranged to be substituted for said slow relay for controlling saidanode circuit, said slow releasing relay having a normally closed set ofcontacts and said second relay having a normally open set of contacts,said anode circuit being completed through said normally closed andthrough said normally open set of contacts.

'7. In a rectifying system, a source of alternating current, a rectifierunit connected to said source of current, an output circuit for saidrectifier unit, a second rectifier unit including a tube having acathode and an anode, a circuit including said cathode electricallyconnected to said source of current, a work circuit including saidanode, resistance units connected to said output circuit, a slowreleasing relay normally connected across said output circuit, a secondrelay connected in circuit to be operated on the operation of said slowreleasing relay, said second relay when operated being substituted incircuit for said slow releasing relay, said anode circuit beingcompleted through contacts of said relays.

In witness whereof, we hereunto subscribe our names this 24th day ofFebruary, 1928.

VIRGIL M. GRAHAM. WVINFRED T. POWELL.

